Iron-gallium Alloys Research Articles

Performance of a modified magnetostrictive energy harvester in mechanical vibration

The field of harvesting electrical energy from ambient vibration has grown with rapid interest. Perpetual source of electrical energy can be extracted from structural vibrations. The paper deals with a technology for scavenging electricity from vibration using iron-gallium alloy. This alloy offers high ductile property and the effect of inverse magnetostriction is also quite high. In this paper, a bending type magnetostrictive prototype energy harvester has been considered. Volume of the used material is 7 × 2 × 42 mm3. Forced & free vibration characteristics have been examined on this prototype. Maximum conversion efficiency of 49% has been achieved at input frequency of 30 Hz.

Влияние отжига в ферромагнитном состоянии на структуру сплава железа с 18 at.% галлия

AbstractThe atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic ( T > T _C) and ferromagnetic ( T < T _C) state. In the first case, the structural state was fixed by quenching from the annealing temperature into water; in the second case, the structural state was obtained by slow cooling. The structural studies of the single-crystal samples were conducted on a four-circle X-ray diffractometer at room temperature. From the X-ray diffraction data, it follows that the alloy, independently on the heat treatment, contains B 2 clusters, i.e., locally ordered regions with the CsCl-type structure observed in alloys of iron with silicon (to 10 at % Si) and aluminum (7 at % Al) before. In addition to the B 2‑clusters, regions with the D 0_3 short-range order are observed in the quenched sample; the sizes of these regions significantly increases after annealing in the ferromagnetic state, i.e., a long-range order forms. The relation of the fine structural changes in the alloy due to various heat treatments with its magnetoelastic and magnetostriction properties is discussed.

Effect of Annealing in a Ferromagnetic State on the Structure of an Fe–18 at % Ga Alloy

The atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic (T > TC) and ferromagnetic (T < TC) state. In the first case, the structural state was fixed by quenching from the annealing temperature into water; in the second case, the structural state was obtained by slow cooling. The structural studies of the single-crystal samples were conducted on a four-circle X-ray diffractometer at room temperature. From the X-ray diffraction data, it follows that the alloy, independently on the heat treatment, contains B2 clusters, i.e., locally ordered regions with the CsCl-type structure observed in alloys of iron with silicon (to 10 at % Si) and aluminum (7 at % Al) before. In addition to the B2‑clusters, regions with the D03 short-range order are observed in the quenched sample; the sizes of these regions significantly increases after annealing in the ferromagnetic state, i.e., a long-range order forms. The relation of the fine structural changes in the alloy due to various heat treatments with its magnetoelastic and magnetostriction properties is discussed.

A magnetostrictive biased magnetic field sensor with geometrically controlled full-scale range

A magnetic field sensor prototype is developed and tested in this work. The device exploits a Galfenol rod, i.e. a giant magnetostrictive Iron-Gallium alloy, integrated with a Fiber Bragg Grating. In particular, the full-scale range of the sensor can be modulated through the exploitation of the geometrically dependent effect of the demagnetizing field. Indeed, it pushes toward higher fields the magnetic saturation by producing a sort of magnetic shield in the material. As a consequence, the geometrical viewpoint is included into the frame of the entire design process, with the aim of investigate how it influences the detectability range and the performance of the sensor. Furthermore, a permanent magnet system providing a DC bias magnetic field has been designed and exploited to allow the device to be able to measure both negative and positive magnetic fields.

Design and Experiments of a Galfenol Composite Cantilever Beam-Driven Magnetostrictive Micro-gripper

The work presents a novel magnetostrictive micro-gripper driven by iron–gallium alloy (Galfenol) composite cantilever beam. The design and operation principles of the given micro-gripper are first introduced. Then, we analyze the magnetic distribution and the jaw displacement of the micro-gripper by theoretical simulations. The performance of magnetostrictive micro-gripper has been tested using the multilevel driving strategy to eliminate the vibration. The proposed micro-gripper can grasp micro-target with a maximum gap of 250 μm, and the maximum exciting current of 1 A. The experimental results demonstrate that the proposed micro-gripper has a simple structure and fast response, suitable for micromanipulation and micro-assembly applications.

Dynamic Model for Magnetostrictive Systems With Applications to Damper Design

Magnetostrictive iron–gallium alloys are able to dissipate mechanical energy via eddy currents and magnetic hysteresis. The mechanically induced eddy current loss is determined by the piezomagnetic coefficient; the hysteresis loss is usually quantified by the phase lag. This study first characterizes these losses for research grade, -oriented, highly textured, polycrystalline $\mathrm{Fe_{81.6}Ga_{18.4}}$ within the structural frequency range (up to 800 Hz). The magnetic biasing is provided by applying a constant current of 500 mA on a pair of electromagnets; the mechanical excitation is a sinusoidal stress wave (3 $\pm$ 0.2 MPa) superimposed on a $-$ 20 MPa constant stress. As stress frequency increases, the piezomagnetic coefficient decreases from 32.27 to 10.33 T/GPa and the phase lag $|\Delta \phi |$ increases from 11.38 $^\circ$ to 43.87 $^\circ$ . A rate-dependent finite element framework decoupling eddy current loss and hysteresis loss is then developed. The model accurately reproduces the experimental results in both quasi-static and dynamic regimes. Guided by the knowledge of material properties and the finite element model, a coil-less and solid-state damper is designed which can attenuate vibrations before they propagate and induce structure-borne noise and damage. Modeling results show that the loss factor of this damper can be continuously tuned from 0 to a maximum value of 0.107 by adjusting the precompression on the magnetostrictive component.

Образование текстуры при прокатке и первичной рекристаллизации в сплаве Fe86Ga14

Fe-Ga alloys possess the increased magnetostriction in comparison with the traditional magnetostrictive materials Fe-Co and Fe-Al and have a number of advantages before magnetostrictive materials based of rare earths. In literature, much attention is paid to structure of Fe81Ga19, as this alloy possesses the greatest magnetostriction in one-phase area. Important condition for achievement of the best functional properties in this material is creation of certain crystallographic texture. However, the substantial difficulty at manufacture of samples and products consists in a high brittleness of alloy at such content of gallium, for this reason the features of formation of crystallographic texture at deformation and recrystallization in this alloy are studied poorly. In this work, the attempt to study influence of various modes of rolling and annealing on structure and magnetic properties of Fe-Ga alloy with the smaller content of Ga is made. The structure and texture of primary recrystallization was studied by means of an electron back-scattering diffraction. Besides field dependences of magnetization were measured, and the amount of grains with the direction of easy magnetization in different samples was estimated by the value of magnetic induction at a defined value of magnetic field on a magnetization curve. The values of magnetostriction increased with increase of volume fraction of the components including the direction of easy magnetization of iron-gallium alloy. Absolute values of magnetostriction did not exceed 50 ppm that is at the level of values for traditional materials, but does not correspond to advantages in magnetostrictive behavior of iron-gallium alloys. Plastic deformation by hot and, especially cold rolling causes great difficulties in connection with a high brittleness of alloy even with the lower value of gallium concentration. Therefore, it is necessary to find new methods of a plastic deformation of alloy or to add the chemical elements improving plastic properties of material.

Structural design and output characteristic analysis of magnetostrictive tactile sensor for robotic applications

A novel magnetostrictive tactile sensor has been designed according to the transduction mechanism of cilia and Villari effect of iron-gallium alloy. The tactile sensor consists of a Galfenol beam, a pair of permanent magnets, a Hall sensor and a signal processing system. Compared with the conventional tactile sensor, our proposed tactile sensor can not only detect the contact-force, but also sense stiffness of an object. The performance and measurement range of tactile sensor have theoretically been analyzed and experimentally investigated. The results have revealed that the sensibility of tactile sensor for sensing force is up to 22.81mV/N at applied bias magnetic field of 2.56kA/m. Moreover, the sensor can effectively discriminate objects with different stiffness. The sensor is characterized by high sensitivity, good linearity, and quick response. It has the potential of being miniaturized and integrated into the finger of a robotic hand to realize force sensing and object recognition in real-time.

Experimental evaluation of external and built-in stress in Galfenol rods

Magnetostrictive properties of Iron-Gallium alloys, such as the saturation of magnetic induction and magnetostriction can be derived from experimental measurements. It is known that, in order to exhibit the largest saturation magnetostriction, Galfenol requires the application of a suitable external compressive stress. In order to avoid a bulky system to provide such stress, a built-in stress could be added to the material through a technological process known as stress annealing. In this paper an experimental method to evaluate the stress applied to Galfenol rods is presented. Then, the method can be exploited either to evaluate the built-in stress or to develop a stress sensor. A concept device exploiting the method and its experimental characterization are presented.

Large stroke and high precision positioning using iron–gallium alloy (Galfenol) based multi-DOF impact drive mechanism

A miniature-positioning device with a large stroke motion has attracted more and more attentions in these years because of the intensive development in precision engineering. In this paper, we have achieved the large stroke actuating and the high precision positioning, as well as realized a multi-degree-of-freedom in-plane motion using the developed Galfenol impact drive mechanism (IDM) actuator. In order to enhance the system robustness, two pieces of U-shape Galfenol (iron–gallium alloy) have been employed as the driving elements with a bias magnetic field contributed by a permanent magnet to generate the swing motion that amplifies the propelling inertia force. The current amplitude modulation has been applied in the precision positioning of the actuator under the quasi-static condition because of the motion step-size fineness. The results show that the actuator is able to achieve a sub-micrometer positioning accuracy that has reached the measurement limit of our setup. Meanwhile, the frequency modulation method has been explored in the large stroke actuation with a high motion speed. We have found out that this design is capable of achieving an accurate positioning without the frequency modulation because of the intrinsic fine step-size of the actuator. In addition, a rectangular in-plane motion has been realized with the image-based control for the multi-degree-of-freedom positioning. The actuator has an inductive impedance with a resistance of 3.796Ω and an inductance of 0.4697mH. Under the present driving ratings, the power consumption is smaller than 1.97W while the reactive power can be ignored. Moreover, the experimental load analysis indicates that the design can achieve a maximum carry-load-to-weight ratio of 6.5.

Comparative study of structural phase transitions in bulk and powdered Fe–27Ga alloy by real-time neutron thermodiffractometry

Phase transformations in an iron–gallium alloy have been analyzed by in situ real-time neutron diffraction in the temperature range from 293 to 1223 K. Two compositionally identical samples were studied: the first was in the as-cast bulk state, and the second was ground into a powdered state. In both samples, the same sequence of structural transitions was recorded on heating with a constant heating rate (D03 → A2 → L12 → D019 → A2), and the same structural state (D03 + L12) was recorded after slow cooling to room temperature. Owing to strong texture in the bulk sample, only diffraction patterns of the powdered sample were treated with the Rietveld method to determine the volume fractions of the coexisting phases, the coefficients of thermal expansion, and the thermal and static atomic disorder parameters. The occupancy of Ga positions and the ordered iron magnetic moment were refined at selected temperatures. The level of microstrain in the crystallites in the initial as-quenched state is small, but it sharply increases in the course of phase transitions when the alloy is heated. The microstrains are high and strongly anisotropic after slow cooling. Generally, phase transformations occur similarly in the powdered and bulk samples, but with a noticeable difference in details. The fulfilled analysis of the bulk and powdered samples allowed the real possibilities of the quantitative neutron diffraction analyses of phase transitions in ferromagnetic ordered alloys to be assessed.

Magnetoelastic auxetic‐like behavior in Galfenol: Experimental data and simulations

Iron–gallium alloy (galfenol) is a body centered cubic (BCC) magnetostrictive alloy that, like many other BCC metals, is auxetic in the ⟨110⟩{100} directions. For compositions of 12–33 at.% gallium, Poisson ratio (ν) values as low as −0.7 are observed along these directions in response to a uniaxial elastic force (tensile tests, resonant ultrasound spectroscopy, etc.). In 2014, Raghunath and Flatau first reported that galfenol also exhibits positive strain in both these directions when the uniaxial force applied along the ⟨110⟩{100} directions is provided solely by a magnetic field, i.e., with no external mechanical/elastic force or stress being applied to the alloy [Raghunath and Flatau, IEEE Trans. Magn. 50(11), 1–4 (2014)]. The observed response is a result of the intrinsic, atomic‐scale, bi‐directionally coupled magnetoelastic properties of these alloys. In this paper, we advance the understanding of the intrinsic atomic‐scale magnetoelastic coupling of the alloy that leads to the observed magnetoelastic auxetic‐like behavior by presenting simulations developed based on density functional theory, which we show match the experimental findings and energy‐based simulations. The elastic anisotropy and the electronic mechanisms that lead to magnetoelastic auxetic‐like behavior in galfenol are discussed.

The hyperfine properties of iron-gallium alloys

The hyperfine properties at Fe site in iron-gallium alloy are calculated using the full-potential linear-augmented-plane-waves method. We have calculated the Fermi contact field (Bhf) and isomer shift (δ) at the Fe site versus the number of neighbouring Ga atoms. We found that Bhf decrease whereas δ increases with increasing number of neighbouring G atom. In addition we have calculated the hyperfine properties of FeGa system with DO3 structure, where various distributions of 4 the Ga atoms in the conventional unit cell are considered (including the regular DO3 structure). We found that the DO3 structure has the lowest energy as compared to the other configurations. The two distinct A and D sites of the ordered DO3 conventional unit cell have two distinct values for Bhf and δ. On changing the atomic arrangement of the Ga atoms within the conventional unit cell, the configuration of the A site is maintained whereas that of the D site becomes imperfect. The contact magnetic hyperfine fields of the D-like sites in the imperfect structures are lower than that of the DO3D site.

1401 並列に配置された弾性支持矩形柱の流力振動特性(OS12-1 噴流・後流・剥離流の解明とその利用)

To develop the power generation system using the magnetostrictive material and the vibration in the flowing water, we focus on transverse-galloping vibration for a rectangular prism with a critical depth section of less than 0.6. Free-vibration tests of two cantilevered rectangular prisms with side ratios of 0.5 and 0.2 in a side-by-side arrangement were performed in a water tunnel to investigate the effects of the gap between two prisms on the flow-induced transverse-galloping vibration and the performance of vibration power generator using an iron-gallium alloy that is a kind of magnetostrictive material. Rectangular prisms with a side ratio of 0.2 vibrate only the characteristic frequency of a prism, and the gap ratio between two prisms has little influence on the response characteristics of vibration. The response characteristics of vibration and the frequency of the rectangular prisms with a side ratio of 0.5 are dependent on gap ratio. The maximum electric power using the rectangular prisms with a side ratio of 0.2 arranged with gap ratio of 0.5 was 10.8 mW at a reduced velocity V_r=2.6.

Orientation dependences of surface morphologies and energies of iron–gallium alloys

We investigated the surface energies of several low-index surfaces of the D03-type FeGa alloys (Galfenol), using density functional theory (DFT) simulations and contact angle measurements. DFT calculations predict that (1) the Ga-covered (110) surface of Galfenol is more stable in the Ga-rich condition, while Ga-covered (001) surface of Galfenol become more favorable in Ga-poor condition; and (2) a full Ga overlayer tends to form on top of Galfenol surfaces regardless their orientation, both in agreement with the experimental observation. We also studied Ga segregation in the bcc Fe matrix in order to explore the possibility of Ga precipitation away from Fe. It was found that the Fe–Ga separation is unlikely to occur since Ga diffusion toward the surface is effectively self-stopped once the Ga overlayers form on the facets.

Design and development of a miniature multi-degree-of-freedom in-plane motor using iron–gallium alloy

This paper presents the design and development of a novel miniature multi-degree-of-freedom motor capable of achieving a 3-DOF in-plane motion. The proposed motor employs the impact drive mechanism that comprises the friction and the inertia force to achieve the self-propelling motion. The motor consists of two U-shape driving elements made of iron–gallium alloy (Galfenol) that is distinguished by its outstanding mechanical property. Meanwhile, the magnetomotive force of a permanent magnet is used not only to increase the friction between the motor and the steel substrate, but also to provide a bias magnetic field within Galfenol. This bias magnetic field enables the motor to generate a swing motion. Although Galfenol has a relatively small strain output compared to other smart materials, the swing motion amplifies the displacement of the inertia mass, which leads to an enlarged inertia force. Two modes of driving current are used to achieve the consistent linear motion and rotation, respectively. The experiment result shows that the new motor can achieve a maximum linear motion velocity of 4.03mm/s and a maximum angular velocity is 15.9°/s. An in-plane motion test shows that the motor is able to track a rectangular trajectory.

Development of a Novel Miniature Shaftless Motor Using Iron–Gallium Alloy (Galfenol)

In this paper, we presented a novel miniature shaftless motor using the impact drive mechanism (IDM) that takes advantage of the friction and the inertia force to achieve the self-propelling motion. The proposed motor uses two U-shaped iron–gallium alloy (Galfenol) rods as the driving elements. Besides Galfenol, the motor consists of one permanent magnet that provides a bias magnetic field within Galfenol. This bias magnetic field helps the motor to generate the swing motion that can amplify the inertia force of the IDM motor. By controlling swing directions of two motor arms through the driving current, the consistent rotation of the motor is accomplished. The experimental result indicates that the proposed motor is able to achieve an angular velocity of 12.74°/s at 230 Hz. Because of the unique design of the motor, the motor can achieve a linear movement, and the result is briefly reported. The objective of future work is to realize an in-plane three-degree-of-freedom motor that can follow a designated trajectory.

Motor-Driven Giant Magnetostrictive Actuator

A typical giant magnetostrictive actuator (GMA) expands a magnetostrictive rod to generate strain by varying the current in the coil that surrounds the magnetostrictive rod. The heat generated by the current deteriorates the GMA performance. In particular, a constant current in the coil is required to produce the desired magnetic field when an output strain should be maintained. The GMA does not produce any mechanical power in this condition, but constant power is being consumed by the excitation coil. This paper presents a new type of motor-driven GMA (MDGMA), which works in a coil-free driven manner. The magnetic field in the iron–gallium alloy (Galfenol), which is a type of magnetostrictive material, is periodically altered by rotating the permanent magnets instead of varying the coil current in the traditional GMA. The proposed MDGMA not only achieves continuous adjustment of the output strain, but can also maintain a constant output strain without consuming any power. In addition, the coil-free design releases the new MDGMA from the heat generated by the excitation coil, which allows the MDGMA to work more stably.

Tensile properties of binary and alloyed Galfenol

Iron–gallium alloys, known as Galfenol, have a unique combination of magneto-mechanical and structural properties that make them an attractive choice for use in robust sensing, actuating, and energy harvesting devices. The high strength and toughness of Galfenol, when compared to traditional active materials such as Terfenol-D and piezoelectric ceramics, are leading to multi-functional (structural and active) applications, such as active-damping engine mounts. Although the toughness of Galfenol is high compared to other functional materials, further improvements in toughness and ductility are beneficial for structural applications. Qualitative analysis of fracture surfaces from binary Galfenol tensile specimens suggests an inverse correlation between the degree of intergranular fracture and the amount of plastic deformation. This implies that modifications to the alloy composition or processing that change the fracture mode from intergranular to transgranular could increase the ductility of the alloy. This paper examines the effect of small additions of tertiary alloying elements (C, Cr, Al) and mixing with low carbon steel (with and without V additions) on the tensile properties and fracture mode of Galfenol. Generally, the addition of alloying elements increased both strength and ductility and changed the fracture mode from intergranular to transgranular fracture.

Performance of improved magnetostrictive vibrational power generator, simple and high power output for practical applications

Vibration based power generation technology is utilized effectively in various fields. Author has invented novel vibrational power generation device using magnetostrictive material. The device is based on parallel beam structure consisting of a rod of iron-gallium alloy wound with coil and yoke accompanied with permanent magnet. When bending force is applied on the tip of the device, the magnetization inside the rod varies with induced stress due to the inverse magnetostrictive effect. In vibration, the time variation of the magnetization generates voltage on the wound coil. The magnetostrictive type is advantageous over conventional such using piezoelectric or moving magnet types in high efficiency and high robustness, and low electrical impedance. Here, author has established device configuration, simple, rigid, and high power output endurable for practical applications. In addition, the improved device is lower cost using less volume of Fe-Ga and permanent magnet compared to our conventional, and its assembly by soldering is easy and fast suitable for mass production. Average power of 3 mW/cm3 under resonant vibration of 212 Hz and 1.2 G was obtained in miniature prototype using Fe-Ga rod of 2 × 0.5× 7 mm3. Furthermore, the damping effect was observed, which demonstrates high energy conversion of the generator.